JP2021172210A - Drive support device of vehicle - Google Patents

Abstract

To appropriately start pre-fill control (pre-load control).SOLUTION: When a preceding vehicle is detected and vehicle velocity Vn is less than pre-fill execution vehicle velocity Vpre, driving support ECU 10 calculates TT target inter-vehicle X (=inter-vehicle deviation ΔD/preceding vehicle relative velocity Vr). The TT target inter-vehicle X represents a temporal allowance required for the inter-vehicle distance to reach a target inter-vehicle distance. When the TT target inter-vehicle X is reduced to a pre-fill start threshold Xpre or less, the driving support ECU 10 transmits a pre-fill control start request to a brake ECU 40 on the conditions that the preceding vehicle relative velocity Vr is equal to or less than a preceding vehicle relative velocity threshold Vrth and preceding vehicle relative acceleration Ar is equal to or less than a preceding vehicle relative acceleration threshold Arth.SELECTED DRAWING: Figure 2

Description

The present invention relates to a vehicle driving support device that causes the own vehicle to follow the preceding vehicle so that the inter-vehicle distance from the own vehicle to the preceding vehicle is maintained at the target inter-vehicle distance.

Conventionally, in order to reduce the driving operation of the driver, a vehicle driving support device that causes the own vehicle to follow the preceding vehicle so that the inter-vehicle distance from the own vehicle to the preceding vehicle is maintained at the target inter-vehicle distance has been known. .. The control that causes the own vehicle to follow the preceding vehicle is called follow-up control. During follow-up control, for example, a target acceleration for making the own vehicle follow the preceding vehicle is calculated, and the engine and the braking device are controlled based on the target acceleration.

In the brake control in the follow-up control, the response delay to the brake request and the operating noise generated by the automatic boosting of the brake oil (brake fluid) become problems. There is a trade-off between the brake response delay time and the operating noise, and it is difficult to balance them. In particular, recently, a collision safety automatic braking function has been installed, and it has been required to increase the amount of brake oil boosted as much as possible in a short time, and along with this, the size of the brake actuator pump has increased. Therefore, the operating noise is deteriorated, and it becomes more difficult to balance the brake response delay and the operating noise.

For example, Patent Document 1 proposes preload control for the purpose of improving brake responsiveness and reducing operating noise. The preload control proposed in Patent Document 1 controls the pump motor to be in the pre-operating state when the drive shaft torque target value is smaller than the driving shaft torque by the running resistance, and decelerates the brake oil in advance. The pressure is increased to the extent that

Japanese Patent No. 4919962

However, in the technique proposed in Patent Document 1, preload control may be performed even when preload control is not actually required. Therefore, there is a concern that the durability of the brake actuator may decrease.

The present invention has been made to solve the above problems, and an object of the present invention is to properly start preload control.

In order to achieve the above object, the features of the present invention are:
By controlling the operation of the drive device (31) and the hydraulic braking device (41, 42), the own vehicle is used as the preceding vehicle so that the inter-vehicle distance from the own vehicle to the preceding vehicle is maintained at the target inter-vehicle distance. In a vehicle driving support device that executes follow-up control, which is control to follow
The actual vehicle-to-vehicle distance acquisition means (21) for acquiring the actual vehicle-to-vehicle distance, which is the distance from the own vehicle to the preceding vehicle, and
Relative speed acquisition means (21) for acquiring the relative speed of the preceding vehicle with respect to the own vehicle, and
The time required for the actual vehicle-to-vehicle distance to reach the target vehicle-to-vehicle distance based on the vehicle-to-vehicle deviation (ΔD), which is the deviation between the target vehicle-to-vehicle distance and the actual vehicle-to-vehicle distance, and the relative speed (Vr). The margin calculation means (10, S13) for calculating the target inter-vehicle distance arrival margin (ΔD / Vr) representing the margin, and
When the relative speed represents the speed in the direction in which the own vehicle approaches the preceding vehicle (S15: Yes), and the target inter-vehicle distance reach margin is reduced to a predetermined value or less (S14: Yes). ) Is provided with preload control means (10, S16, 40) for increasing the oil pressure of the hydraulic braking device in advance in preparation for braking operation.

The vehicle driving support device of the present invention controls the operation of the drive device and the hydraulic braking device to make the own vehicle the preceding vehicle so that the inter-vehicle distance from the own vehicle to the preceding vehicle is maintained at the target inter-vehicle distance. Follow-up control, which is control to follow, is executed. The drive device is a device that generates a driving force for traveling a vehicle, and is, for example, an engine, a traveling motor, or a hybrid driving device that combines them. The hydraulic brake device is, for example, a type of brake device capable of increasing the brake pressure (flood control) by operating a pump.

During the execution of the follow-up control, a brake request for keeping the inter-vehicle distance at the target inter-vehicle distance is generated, and the hydraulic braking device operates according to this brake request. In this case, the delay in responding to the brake request and the operating noise generated by the automatic pressurization of the brake oil become problems. Therefore, the vehicle driving support device of the present invention implements preload control that increases the oil pressure of the hydraulic braking device in advance in preparation for braking operation. In this case, it is necessary to start the preload control at an appropriate timing. In order to do so, the vehicle driving support device includes an actual vehicle-to-vehicle distance acquisition means, a relative speed acquisition means, a margin calculation means, and a preload control means.

The actual vehicle-to-vehicle distance acquisition means acquires the actual vehicle-to-vehicle distance, which is the distance from the own vehicle to the preceding vehicle. For example, the actual vehicle-to-vehicle distance acquisition means measures the actual vehicle-to-vehicle distance using a radar sensor, a camera sensor, or the like.

The relative speed acquisition means acquires the relative speed of the preceding vehicle with respect to the own vehicle. For example, the relative speed acquisition means measures the relative speed with a radar sensor, a camera sensor, or the like.

The margin calculation means is a target that expresses the time margin required for the actual inter-vehicle distance to reach the target inter-vehicle distance based on the inter-vehicle deviation, which is the deviation between the target inter-vehicle distance and the actual inter-vehicle distance, and the relative speed. Calculate the inter-vehicle distance reach margin. For example, the target inter-vehicle distance arrival margin can be obtained by using the value obtained by dividing the inter-vehicle deviation by the relative speed.

For example, when the preceding vehicle moves away from the own vehicle, the operation of the hydraulic braking device is not started, but when the own vehicle approaches the preceding vehicle, the hydraulic braking device operates from the middle of the operation. May generate braking force. The preload control means increases the oil pressure in advance within a range in which the braking force is substantially not generated (referred to as preload control) in preparation for the braking operation by the hydraulic braking device.

For example, the preload control means operates the pump of the brake actuator to increase the oil pressure of the wheel cylinder to a predetermined pressure. By increasing the oil pressure in advance in this way, the workload of the hydraulic braking device when generating the braking force is reduced, the response delay from the braking request to the actual generation of the braking force, and the braking at the time of the braking request. It is possible to reduce the operating noise generated by the automatic pressurization of the oil.

In this case, it is necessary to make the timing to start the preload control appropriate. Therefore, the preload control means is a hydraulic braking device when the relative speed represents the speed in the direction in which the own vehicle approaches the preceding vehicle and the margin for reaching the target inter-vehicle distance drops to a predetermined value or less. Increase the oil pressure in advance in preparation for braking.

Therefore, according to the present invention, preload control can be started properly. As a result, unnecessary preload control is reduced, and the durability of the hydraulic braking device can be improved. In addition, the frequency of operation noise can be reduced.

In the above description, in order to help the understanding of the invention, the reference numerals used in the embodiments are attached in parentheses to the constituent elements of the invention corresponding to the embodiment. It is not limited to the embodiment defined by.

It is a schematic system block diagram of the driving support device of the vehicle which concerns on this embodiment. It is a flowchart which shows the prefill control start request routine. It is a figure which shows the TT target vehicle distance according to the situation of own vehicle and the preceding vehicle (when the TT target vehicle distance is plus). It is a figure which shows the TT target vehicle distance according to the situation of own vehicle and the preceding vehicle (when the TT target vehicle distance is minus).

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic system configuration diagram of the vehicle driving support device of the present embodiment.

The vehicle driving support device of the present embodiment includes a driving support ECU 10. The driving support ECU 10 is an electronic control device for assisting the driver's driving, and includes a microcomputer as a main part. ECU is an abbreviation for Electronic Control Unit. The driving support ECU 10 of the present embodiment has follow-up control that causes the own vehicle to follow the preceding vehicle so that the inter-vehicle distance from the own vehicle to the preceding vehicle is maintained at the target inter-vehicle distance, and if the preceding vehicle does not exist, the driving support ECU 10 has follow-up control. It supports the driver's driving by implementing constant speed control that causes the own vehicle to run at a constant speed at the set vehicle speed set by the driver. Such driving assistance control is commonly referred to as adaptive cruise control (ACC).

The driving support ECU 10 is connected to the preceding vehicle sensor unit 21, the operation switch 22, and the vehicle speed sensor 23. The preceding vehicle sensor unit 21 has a function of acquiring information on a preceding vehicle existing in front of the own vehicle, and includes, for example, a radar sensor 21a and a camera sensor 21b.

The preceding vehicle sensor unit 21 determines the presence or absence of the preceding vehicle based on the target information detected by the radar sensor 21a and the target information detected by the camera sensor 21b, and from the own vehicle to the preceding vehicle. The distance (called the distance between the preceding vehicles), the relative speed of the own vehicle with the preceding vehicle (called the relative speed of the preceding vehicle), the relative acceleration of the own vehicle with the preceding vehicle (called the relative acceleration of the preceding vehicle), etc. are predetermined cycles. Calculate with. The preceding vehicle sensor unit 21 calculates the presence / absence of the preceding vehicle, the distance between the preceding vehicles, the relative speed of the preceding vehicle, and the relative acceleration of the preceding vehicle (these are referred to as preceding vehicle information), and the preceding vehicle information is the calculation result. Is transmitted to the driving support ECU 10.

The preceding vehicle sensor unit 21 does not necessarily have to include both the radar sensor 21a and the camera sensor 21b, and may be configured to include either one or the other sensor. good. Further, the driving support ECU 10 may be provided integrally with the preceding vehicle sensor unit 21.

The operation switch 22 is a switch that is operated by the operation of the driver, and outputs this operation signal to the operation support ECU 10. The operation switch 22 outputs the following operation signals.
(1) On / off of driving support function (2) Switching between constant speed control mode and follow-up control mode (3) Setting vehicle speed for constant-speed driving (4) Setting inter-vehicle distance in follow-up control mode (long / medium)・ Short)

In the constant speed control mode, constant speed control is performed. In the follow-up control mode, follow-up control is performed when the preceding vehicle exists, and constant speed control is performed when the preceding vehicle does not exist (when the preceding vehicle to be followed-controlled is not detected). The constant speed control is a control for driving the own vehicle at a constant speed at a set vehicle speed set by the operation switch 22. The follow-up control is a control that causes the own vehicle to follow the preceding vehicle so that the inter-vehicle distance from the own vehicle to the preceding vehicle is maintained at the target inter-vehicle distance based on the preceding vehicle information. When constant speed control or follow-up control is performed, the driver does not need to operate the accelerator pedal.

The operation switch 22 does not have to be configured to achieve the above function by one operator (lever or the like), and may be configured to realize the above function by combining a plurality of controls. The driving support ECU 10 stores parameters (vehicle speed for constant speed traveling, target inter-vehicle distance during follow-up control, etc.) set by the driver using the operation switch 22 in the non-volatile memory. The vehicle speed for constant speed traveling set by the driver using the operation switch 22 is called a set vehicle speed Vset.

The vehicle speed sensor 23 outputs a detection signal indicating the vehicle speed Vn of the own vehicle.

The driving support ECU 10 is connected to the engine ECU 30 and the brake ECU 40 so as to be able to transmit and receive signals to each other by a CAN (Controller Area Network). The engine ECU 30 is connected to various sensors 33 required for controlling the engine 31 and controlling the transmission 32. The engine ECU 30 performs fuel injection control, ignition control, and intake air amount control of the engine 31 based on the required driving force. Further, the engine ECU 30 controls the shift of the transmission 32 based on the shift-up line and the shift-down line that are predetermined with respect to the vehicle speed and the throttle opening degree.

The driving support ECU 10 calculates the target acceleration of the own vehicle at the time of executing the constant speed control and the follow-up control, and further accelerates the own vehicle at this target acceleration (deceleration in which the target acceleration becomes a negative value). Calculate the required driving force F * (including negative values, that is, the required braking force) required for (including). The driving support ECU 10 transmits this required driving force F * to the engine ECU 30. The engine ECU 30 controls the engine 31 and the transmission 32 according to the required driving force F *. When the required driving force F * becomes a value that requires a large braking force and the demand cannot be met by the engine 31 and the transmission 32 alone, the engine ECU 30 causes the brake ECU 40 to generate the shortage by the hydraulic brake. And send a brake request. When constant speed control is implemented, the target acceleration for constant speed running is calculated so that a braking force sufficient to require a hydraulic brake is not required.

The brake ECU 40 includes a microcomputer as a main part, and is connected to the brake actuator 41. The brake actuator 41 is provided in a hydraulic circuit between a master cylinder (not shown) that pressurizes brake oil (brake fluid) by the pedaling force of a brake pedal and a friction brake mechanism 42 provided on the left, right, front and rear wheels. The friction brake mechanism 42 includes a brake disc 42a fixed to the wheels and a brake caliper 42b fixed to the vehicle body, and operates the wheel cylinder built in the brake caliper 42b by the hydraulic pressure supplied from the brake actuator 41. The brake pad is pressed against the brake disc 42a to generate a braking force (friction braking force). The brake actuator 41 is provided with a solenoid valve for switching the flow path, a pump for boosting (electric pump), etc., and by operating the pump, the increased hydraulic pressure is applied to the wheel cylinder without the need for pedaling force of the brake pedal. It is configured to be able to supply. Such a brake actuator is general, and for example, the one shown in Patent Document 1 can be appropriately adopted.

The brake ECU 40 is connected to various sensors 43 required for controlling the brake actuator 41. The brake ECU 40 controls the operation of the brake actuator 41 based on the required braking force to generate a friction braking force on the wheels.

Next, the follow-up control and the constant speed control performed by the driving support ECU 10 will be described. Since the follow-up control and the constant speed control are generally known, an example thereof will be briefly described here.
<Follow-up control>
The driving support ECU 10 sets the target inter-vehicle distance based on the vehicle speed Vn detected by the vehicle speed sensor 23 and the set inter-vehicle distance (long / medium / short) set and stored by the driver.

As shown in the following equations (1) and (2), the driving support ECU 10 calculates the acceleration side follow-up target acceleration Afollow1 * and the deceleration side follow-up target acceleration Afollow2 *. When the deceleration side follow-up target acceleration Afollow2 * becomes a negative value (Afollow2 * <0 m / s ² ), the driving support ECU 10 adopts the deceleration side follow-up target acceleration Afollow2 * as the follow-up target acceleration Afollow *. (Afollow * = Afollow2 *), otherwise, the acceleration side follow-up target acceleration Afollow1 is adopted as the follow-up target acceleration Afollow * (Afollow * = Afollow1 *).

Afollow1 * = ((−ΔD × K1) + (Vr × K2)) × Ka ・ ・ ・ (1)
Afollow2 * = ((−ΔD × K1) + (Vr × K2)) ・ ・ ・ (2)

Here, ΔD is the inter-vehicle deviation, K1 and K2 are gains, Vr is the relative speed of the preceding vehicle, and Ka is the acceleration side gain.

The inter-vehicle deviation ΔD is a value obtained by subtracting the actual inter-vehicle distance from the preceding vehicle from the target inter-vehicle distance. Therefore, in a situation where the actual inter-vehicle distance of the preceding vehicle is longer than the target inter-vehicle distance, the inter-vehicle deviation ΔD becomes a negative value (−ΔD is a positive value), and works in the direction of increasing the target acceleration Afollow * for tracking. Hereinafter, the actual inter-vehicle distance of the preceding vehicle may be referred to as an actual inter-vehicle distance.
The gains K1 and K2 are positive values for adjustment, and may be fixed values or values adjusted by other parameters.
The relative speed Vr of the preceding vehicle is the relative speed of the preceding vehicle with respect to the own vehicle, and is a value obtained by subtracting the vehicle speed of the own vehicle from the vehicle speed of the preceding vehicle. Therefore, in a situation where the preceding vehicle moves away from the own vehicle, the relative speed Vr of the preceding vehicle becomes a positive value and acts in the direction of increasing the tracking target acceleration Afollow *. Hereinafter, the relative speed Vr of the preceding vehicle may be simply referred to as the relative speed Vr.

The acceleration side gain Ka is a positive value for adjusting the magnitude of the acceleration side follow-up target acceleration Afollow1 with respect to the deceleration side follow-up target acceleration Afollow2.

The driving support ECU 10 calculates an acceleration deviation ΔA (= Afollow * −An), which is a deviation between the target acceleration Afollow * for tracking and the actual acceleration An, which is the actual acceleration of the own vehicle, and is based on this acceleration deviation ΔA. Calculate the required driving force F *. For example, as shown in the following equation (3), the driving support ECU 10 obtains a value obtained by multiplying the acceleration deviation ΔA by the gain K3 and adding the required driving force F * (n-1) one calculation cycle before. Set to the required driving force F *.
F * = (Afollow * -An) x K3 + F * (n-1) ... (3)

The driving support ECU 10 calculates the required driving force F * in a predetermined calculation cycle, and supplies the calculated required driving force F * to the engine ECU 30 each time. As a result, the driving force is controlled so that the own vehicle accelerates (including deceleration) at the target acceleration Afollow * for tracking. Therefore, the own vehicle can be driven at an acceleration suitable for follow-up control. The actual acceleration An may be acquired by differentially calculating the vehicle speed Vn, or may be acquired from the detection value of the front-rear acceleration sensor by providing a front-rear acceleration sensor (not shown) on the vehicle body. You may.

When a large braking force is required and the engine 31 and the transmission 32 alone cannot meet the demand, the engine ECU 30 transmits a brake request to the brake ECU 40 so that the shortage is generated by the hydraulic brake. This braking requirement contains information representing the required braking force.

Upon receiving the brake request, the brake ECU 40 controls the operation of the brake actuator 41 so as to generate the required braking force, and supplies the oil pressure increased by the pump to the wheel cylinder. As a result, the brake pad is pressed against the brake disc to generate a braking force (friction braking force), and the own vehicle decelerates.

In the follow-up control, a certain margin is provided so that the movement of the vehicle does not react sensitively to the inter-vehicle deviation ΔD and the relative speed Vr.

<Constant speed control>
The driving support ECU 10 performs constant speed control when the preceding vehicle does not exist. The driving support ECU 10 is based on the vehicle speed Vn detected by the vehicle speed sensor 23 and the set vehicle speed Vset set by the driver using the operation switch 22, as shown in the following equation (4), the target acceleration for constant speed driving. Calculate Aconst *.
Aconst * = (Vset-Vn) x K4 ... (4)

Here, K4 is an acceleration gain for constant speed traveling, and is set to a positive value according to the vehicle speed Vn. The constant-speed running acceleration gain K4 is set to a value smaller when the vehicle speed Vn is high than when it is low. When the vehicle speed deviation (Vset-Vn) of the first term on the right side of the equation (4) is positive, the target acceleration Aconst * for constant speed driving that works in the direction of accelerating the own vehicle is calculated, and the vehicle speed deviation (Vset-Vn). If is negative, the target acceleration Aconst * for constant-speed traveling that works in the direction of decelerating the own vehicle is calculated.

The driving support ECU 10 calculates an acceleration deviation ΔA (= Accelt * −An), which is a deviation between the target acceleration Aconst * for constant-speed traveling and the actual acceleration An, which is the actual acceleration of the own vehicle, and obtains this acceleration deviation ΔA. The required driving force F * is calculated based on this. For example, as shown in the following equation (5), the driving support ECU 10 obtains a value obtained by multiplying the acceleration deviation ΔA by the gain K5 and adding the required driving force F * (n-1) one calculation cycle before. Set to the required driving force F *.
F * = (Aconst * -An) x K5 + F * (n-1) ... (5)

The driving support ECU 10 calculates the required driving force F * in a predetermined calculation cycle, and supplies the calculated required driving force F * to the engine ECU 30 each time. As a result, the driving force is controlled so that the own vehicle accelerates (including deceleration) at the target acceleration A *. Therefore, the own vehicle can be driven at an acceleration suitable for constant speed control.

<Prefill control>
The driving support ECU 10 performs prefill control in parallel with the follow-up control. The prefill control is a control in which the brake oil pressure is increased to such an extent that the own vehicle does not decelerate in advance before the hydraulic brake is activated by the follow-up control, and corresponds to the preload control of the present invention. The necessity of prefill control will be described below.

In the brake control in the follow-up control, the response delay to the brake request transmitted to the brake ECU 40 and the operating noise generated by the automatic boosting of the brake oil are problems. Upon receiving the brake request, the brake ECU 40 starts the pump of the brake actuator 41 to increase the oil pressure, and presses the brake pad against the brake disc by the pressure increase. The response delay means a time delay from when the brake request is transmitted to the brake ECU 40 until the brake pad hits the brake disc.

This response delay is difficult to avoid due to the configuration of the brake parts of the vehicle. By increasing the motor rotation speed of the pump provided in the brake actuator 41 in order to make up for the delay, the response delay time can be shortened. However, as a trade-off, the operating noise increases.

There are two main transmission paths for operating noise. One of them is a path in which the vibration of the brake actuator 41 itself is transmitted to the body via the bracket. The other is a path through which vibration caused by the pulsation of brake oil passing through the brake pipe is transmitted to the body. These two vibrations are proportional to the motor speed of the pump. Therefore, as the rotation speed of the motor is increased in an attempt to improve the responsiveness of the brake, the above-mentioned vibration is amplified, causing deterioration (increase) of the operating noise.

In this way, there is a trade-off between the brake response delay and the operating noise. Prefill control is known as one method for improving this trade-off relationship. The prefill control is a control in which the brake oil pressure is increased to the extent that the own vehicle does not decelerate in advance before the hydraulic brake is started by the follow-up control. In other words, the amount of brake oil required from the start of the brake actuator pump to the time when the brake pad hits the brake disc is filled in the wheel cylinder in advance (before the hydraulic brake is started). It is control. As a result, the response delay time can be shortened without increasing the motor rotation speed (without deteriorating the operating noise).

However, the prefill control is started at an appropriate timing because it produces an operating noise, the durability of the brake actuator 41 is reduced, and the prefill control must be performed before the hydraulic brake is started. Need to be done.

Therefore, in the present embodiment, the start timing of the prefill control is set as follows.

FIG. 2 is a flowchart showing a prefill control start request routine. The operation support ECU 10 executes this prefill control start request routine during execution of the ACC.

When the driving support ECU 10 activates the prefill control start request routine, it first determines in step S11 whether or not the preceding vehicle is detected. If the preceding vehicle is not detected, prefill control is not performed because constant speed control is being performed. Therefore, the driving support ECU 10 repeatedly executes the determination process of step S11 until the preceding vehicle is detected.

If the preceding vehicle is detected, follow-up control is performed. When the preceding vehicle is detected (S11: Yes), the driving support ECU 10 advances the process to step S12, and the current vehicle speed Vn detected by the vehicle speed sensor 23 is less than the preset prefilled vehicle speed Vpre. Determine if it exists. When the vehicle speed is high, background noise (so-called background noise) is large, and it is difficult for the occupant to hear the operating noise of the brake actuator 41 (it does not bother him). Therefore, prefill control should not be performed when the vehicle speed is high. The prefilling vehicle speed Vpre is set to a boundary value at which the operating sound of the brake actuator 41 cannot be heard by the occupant. For example, the vehicle speed Vpre for prefilling is 45 km / h.

When the driving support ECU 10 determines that the vehicle speed Vn is equal to or higher than the prefilling vehicle speed Vpre (S12: No), the process is returned to step S11 and the above-described process is repeated. On the other hand, when the vehicle speed Vn is less than the prefilling vehicle speed Vpre, the driving support ECU 10 proceeds to the process in step S13.

The driving support ECU 10 calculates the TT target vehicle-to-vehicle distance X in step S13. The TT target inter-vehicle distance X is a value obtained by dividing the inter-vehicle deviation ΔD by the relative speed Vr of the preceding vehicle, as shown in the following equation (6).
TT Target vehicle-to-vehicle distance X = Inter-vehicle deviation ΔD / Relative velocity of the preceding vehicle Vr ・ ・ ・ (6)

The inter-vehicle deviation ΔD is a value obtained by subtracting the actual inter-vehicle distance (actual inter-vehicle distance) from the target inter-vehicle distance. The relative speed Vr of the preceding vehicle is the relative speed of the preceding vehicle with respect to the own vehicle, and is a value obtained by subtracting the vehicle speed of the own vehicle from the vehicle speed of the preceding vehicle.

The TT target vehicle-to-vehicle distance X (Time to target vehicle-to-vehicle distance) is an index value indicating the time margin required to reach the target vehicle-to-vehicle distance, and corresponds to the target vehicle-to-vehicle distance reaching margin of the present invention.

The case where the operation of the hydraulic brake is started in the follow-up control is the case where the relative speed Vr of the preceding vehicle becomes a negative (minus) value. Therefore, the prefill control performed prior to the hydraulic brake is performed on the premise that the relative speed Vr of the preceding vehicle becomes a negative value.

The relationship between the own vehicle and the preceding vehicle can be classified as follows according to the value of the TT target vehicle-to-vehicle distance X.
(1) When the TT target vehicle-to-vehicle distance X is positive: The own vehicle is farther than the target vehicle-to-vehicle distance from the preceding vehicle.
(2) When the TT target vehicle-to-vehicle distance X is negative: The own vehicle is closer than the target vehicle-to-vehicle distance to the preceding vehicle.

FIG. 3 shows the relationship between the own vehicle and the preceding vehicle when the TT target vehicle-to-vehicle distance X is positive, and FIG. 4 shows the relationship between the own vehicle and the preceding vehicle when the TT target vehicle-to-vehicle distance X is negative. Represents. The smaller the TT target vehicle-to-vehicle distance X, the higher the urgency of operating the brake.

For example, in scenes 1 to 4 of FIG. 3, the TT target vehicle-to-vehicle distance X decreases in the order of scene 1 → scene 2 → scene 3 → scene 4 (the degree of urgency increases).

Scene 1 represents a scene in which the brake of the own vehicle is activated during the follow-up control to catch up with the preceding vehicle traveling at a low speed at a distance. For example, when the preceding vehicle sensor unit 21 cannot detect the preceding vehicle while traveling on a curved road, the brake may be activated. Scene 2 shows a scene in which the preceding vehicle applies the brake during the follow-up control with a slight distance between the vehicles, and the brake of the own vehicle operates accordingly. Scene 3 represents a scene in which the brake of the own vehicle is activated during follow-up control in which the inter-vehicle distance is small. Scene 4 shows a scene in which the preceding vehicle applies the brake during the follow-up control in a state where the inter-vehicle deviation is small, and the brake of the own vehicle operates accordingly.

Further, in scenes 5 to 7 of FIG. 4, the TT target vehicle-to-vehicle distance X is smaller than that of scenes 1 to 4 shown in FIG. 3, and decreases in the order of scene 5 → scene 6 → scene 7 (high urgency). Become).

Scene 5 shows a scene in which the preceding vehicle applies the brake during the follow-up control in a state where the inter-vehicle distance is slightly reduced, and the brake of the own vehicle operates accordingly. In scene 6, another vehicle interrupts between the own vehicle and the preceding vehicle during follow-up control at an appropriate inter-vehicle distance, and the own vehicle approaches the interrupting vehicle (recognized as a new preceding vehicle) and self. It represents a scene in which the vehicle brakes are activated. In scene 7, another vehicle interrupts between the own vehicle and the preceding vehicle at a position close to the own vehicle during the follow-up control at an appropriate inter-vehicle distance, recognizes this interrupted vehicle as a new preceding vehicle, and owns the vehicle. It represents the scene where the brake was activated.

Therefore, by using the value of the TT target vehicle-to-vehicle distance X, the timing at which the brake starts to operate can be accurately predicted by the follow-up control, and thereby the start timing of the prefill control can be set appropriately.

Returning to the description of the prefill control start request routine of FIG. When the driving support ECU 10 calculates the TT target vehicle-to-vehicle distance X, the process proceeds to step S14 to determine whether or not the TT target vehicle-to-vehicle distance X is equal to or less than the prefill start threshold value Xpre. The prefill start threshold value Xpre is a value of the TT target vehicle-to-vehicle distance X that is estimated to start prefill control, and is set in advance by experiments or the like. When the TT target vehicle-to-vehicle distance X is larger than the prefill start threshold value Xpre, the driving support ECU 10 returns the process to step S11 and repeats the above-described process.

When the driving support ECU 10 repeats such a process and determines that the TT target vehicle-to-vehicle distance X is equal to or less than the prefill start threshold value Xpre (S14: Yes), the process proceeds to step S15, and the preceding vehicle relative speed Vr is relative to the preceding vehicle. It is determined whether or not the speed threshold is Vrth or less and the relative acceleration Ar of the preceding vehicle is equal to or less than the relative acceleration threshold Art of the preceding vehicle. The preceding vehicle relative acceleration Ar is a differential value of the preceding vehicle relative velocity Vr. Both the preceding vehicle relative speed threshold value Vrth and the preceding vehicle relative acceleration threshold value Arth are negative values.

When the relative speed Vr of the preceding vehicle is positive, the own vehicle does not collide with the preceding vehicle due to a physical phenomenon, and it is unlikely that the vehicle will start decelerating. On the other hand, the value of the TT target vehicle-to-vehicle distance X alone cannot be used to determine whether the movement of the preceding vehicle is on the negative side or the positive side. For example, in a case where the relative speed Vr of the preceding vehicle is + 5 km / h (moving away) and the inter-vehicle deviation ΔD is + 5 m (close) (referred to as case A), the relative speed Vr of the preceding vehicle is -5 km / h (approaching). Consider a case (called case B) in which the inter-vehicle deviation ΔD is -5 m (separated). The TT target vehicle-to-vehicle distance X is the same value "1" in both case A and case B.

In case B, there is a high possibility that the own vehicle decelerates with respect to the decelerated preceding vehicle, but in case A, there is a high possibility that the own vehicle accelerates, and it is not necessary to perform prefill control. Therefore, in the present embodiment, the scene in which the prefill control should be performed is limited by providing the process of step S15. In this case, since the scene is limited not only by the relative speed Vr of the preceding vehicle but also by the relative acceleration Ar of the preceding vehicle, the relative movement between the own vehicle and the preceding vehicle can be grasped appropriately and quickly, and the prefill. It is possible to prevent the start of control from being delayed.

When the operation support ECU 10 determines "No" in step S15, the operation returns to step S11. On the other hand, if it is determined as "Yes", the driving support ECU 10 advances the process to step S16 and transmits a prefill control start request to the brake ECU 40. In response to this prefill control start request, the brake ECU 40 starts the prefill control. In this case, the brake ECU 40 rotates the pump of the brake actuator 41 at the prefill rotation speed to increase the oil pressure of the wheel cylinder. As a result, the wheel cylinder is filled with the amount of brake oil required for the brake pads to hit the brake discs to the extent that deceleration does not occur. The brake ECU 40 maintains the oil pressure of the wheel cylinder at a predetermined pressure by prefill control until the brake request is received.

As a result, the workload of the brake actuator 41 when generating the braking force is reduced, the response delay from the braking request to the actual generation of the braking force, and the operation generated by the automatic pressure increase of the brake oil at the time of the braking request. Sound can be reduced.

When the operation support ECU 10 transmits the prefill control start request to the brake ECU 40, the operation support ECU 10 ends the prefill control start request routine.

According to the vehicle driving support device of the present embodiment described above, in carrying out the prefill control, the inter-vehicle deviation ΔD is divided by the relative speed Vr of the preceding vehicle to calculate the TT target inter-vehicle distance X, and the TT target inter-vehicle distance X is calculated. Prefill control start request when the relative speed Vr of the preceding vehicle is equal to or less than the relative speed threshold Vrth of the preceding vehicle and the relative acceleration Ar of the preceding vehicle is equal to or less than the relative acceleration threshold Arth of the preceding vehicle. Is transmitted to the brake ECU 40. Therefore, the prefill control can be started at an appropriate timing.

As a result, unnecessary prefill control is reduced, and the durability of the hydraulic braking device can be improved. In addition, the frequency of generation of operating noise of the brake actuator can be reduced. Further, it is possible to reduce the case where the prefill control is delayed with respect to the main brake (brake by the follow-up control), that is, the prefill control cannot be performed.

Although the vehicle driving support device according to the present embodiment has been described above, the present invention is not limited to the above embodiment, and various modifications can be made without departing from the object of the present invention.

For example, in step S15, it may be determined that the relative speed Vr of the preceding vehicle is at least the relative speed threshold Vrth of the preceding vehicle, and the relative acceleration Ar of the preceding vehicle is necessarily equal to or less than the relative acceleration threshold Arth of the preceding vehicle. It is not necessary to provide.

10 ... Driving support ECU, 21 ... Leading vehicle sensor unit, 21a ... Radar sensor, 21b ... Camera sensor, 22 ... Operation switch, 23 ... Vehicle speed sensor, 30 ... Engine ECU, 31 ... Engine, 40 ... Brake ECU, 41 ... Brake Actuator, 42 ... Friction brake mechanism, Vn ... Vehicle speed, Vpre ... Prefilled vehicle speed, ΔD ... Inter-vehicle deviation, Vr ... Leading vehicle relative speed, Vrth ... Leading vehicle relative speed threshold, Ar ... Leading vehicle relative acceleration, Arth ... Leading vehicle relative Acceleration threshold, X ... TT target vehicle distance, Xpre ... Prefill start threshold.

Claims (1)

Follow-up control is a control that controls the operation of the drive device and the hydraulic braking device to make the own vehicle follow the preceding vehicle so that the inter-vehicle distance from the own vehicle to the preceding vehicle is maintained at the target inter-vehicle distance. In the driving support device of the vehicle to be executed
An actual vehicle-to-vehicle distance acquisition means for acquiring an actual vehicle-to-vehicle distance, which is the distance from the own vehicle to the preceding vehicle,
A relative speed acquisition means for acquiring the relative speed of the preceding vehicle with respect to the own vehicle, and
Based on the inter-vehicle deviation, which is the deviation between the target inter-vehicle distance and the actual inter-vehicle distance, and the relative speed, the target inter-vehicle distance represents the time margin required for the actual inter-vehicle distance to reach the target inter-vehicle distance. A margin calculation means for calculating the distance arrival margin, and
When the relative speed represents the speed in the direction in which the own vehicle approaches the preceding vehicle and the margin for reaching the target inter-vehicle distance is reduced to a predetermined value or less, the oil pressure of the hydraulic braking device is applied. A vehicle driving support device equipped with a preload control means that increases in advance in preparation for braking.

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